Coded track circuit signaling system



Feb. 22, 1944. N. o. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM 11Sheets-Sheet 1 Filed Aug 19, 1942 1$ a. T m 9. co gmw g u u ,u 561% Feb.22, 1944. N. D. PRESTON- CODE'D TRACK CIRCUIT SIGNALING SYSTEM FiledAug. 19, 1942 ll Sheets-Sheet 2 QFU mm I5 baa Feb. 22, 1944. N. D.PRESTON 2,342,439

GODED TRACK CIRCUIT SIGNALING SYSTEM Filed Aug. 19, 1942 11 Sheets-Sheets 3 m8: u 4 n; u u v We @114 mm 3 I I L 82 I Is T At Feb. 22, 1944.PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM Filed Aug. 19, 1942 llSheets-Sheet 4 1944- N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEMFiled Aug. 19, 1942 11 Sheets-Sheet 5 Feb. 22, 1944. N. D. PRESTON CODEDTRACK CIRCUIT SIGNALING SYSTEM Filed Aug. 19, 1942 ll Sheets-Sheet 6Feb. 22, 1944. N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM FiledAug. 19, 1942 11 Sheets-Sheet 7 1944- N. D. PRESTON QODED TRACK CIRCUITSIGNALING SYSTEM Filed Aug. 19, 1942 ll Sheets-Sheet 8 a 25 JL JL tfim Fb- 22, 1944. N. n PREsToM CODED TRACK CIRCUIT SIGNALING SYSTEM FiledAug. 19, 1942 ll Sheets-Sheet 10 1944- N. D. PRESTON CODED TRACK CIRQUIT SIGNALING SYSTEM Filed Au 19, 1942 '11 Sheets-Sheet 11 II J ITENTORI MM E AL nS n Patented Feb. 22, 1944 ,CODED TRACK CIRCUIT SIGNALINGSYSTEM Neil D. Preston,

Rochester, N. Y., assignor to General Railway Signal Company, Rochester,N

Application August 19, 1942, Serial No. 455,328 (Cl. 246-3) 53 Claims.

This invention relates to coded track circuit signaling systems forrailroads, and more particularly to a centralized trafiic control (C. T.C.) system for single track railroads.

In connection with the application of the conventional coded trackcircuit to single track railroads or like stretches of' track havingsignals governing train movement in both directions, the direction inwhich the coded pulses are transmitted over the track rails of varioustrack circuits for governing the indications of the associated signalshas to be selected or governed to conform with the direction of trainmovement desired; and one method of determining the desired direction oftrack circuit coding, as disclosed, for example, in my priorapplication, Ser. No. 439,520, filed April 18, 1942, is by thesupervisory manual control of the C. T. C. system used for controllingthe clearing of the signals and also if desired for governing the poweroperation of track switches. In certain respects the present inventionis in the nature of a variation or modification of this priordisclosure; and it is not intended to make ter disclosed in said priorapplication.

The primary object of the present invention may be said to be theprovision of a simple organization of coded track circuits incombination with a C. T. C. system, preferably of the code type, whichwill aiford all the desired safety and facility for train movement onsingle track railroads, or for like stretches of track having traflic inboth directions, the essential functions being performed without the useof line wires except as may be required for the transmission of controlsand indications between a control office and various field locationsover the C. T. C. system.

Generally speaking, and without attempting to define the nature andscope of this invention, and considering one embodiment of the inventionin its application to a typical single track railroad having passingsidings, it is proposed to employ the same manual controls of the C. T.C. system which are used to control the clearing of the signalsgoverning train movement into and out of the stretches of single trackfor determining the direction of coding in the several track sections,leaving the coding of these track sections in the directioncorresponding with the last train movement, and providing for theautomatic reversal of such existing direction of track circuit codingwhenever desired for opposing train move ments by merely initiatingcoding operation of any claim herein to subject matthe track circuits inthe opposite direction to overpower and discontinue coding in theexisting direction. For example, after a trainhas travelled through astretch of single trackbetween the ends of passing sidings in one direction, and has left the track circuits of the stretch coding in adirection for following train movements, 2. manual control for clearingthe opposing starting or head-block signal, when exercised over the C.T. C. system, also actsto initiate track circuit coding at the oppositeend of the stretch, which overcomes or bucks down, so to speak, thetrack circuit coding in the existing direction in the track circuits ofthe stretch in turn, thereby causing clearing of the head-block signaland intermediate signals for the newdesired direction of train movement.7

Considering more specifically the means employed, there is a codesending meansfor each end of the stretch of a single track between theends of passing sidings which once set into operation continues inoperation until restored by code pulses received over the track railsfrom the opposite end; and when a manual control is exercised over theCH1. C. system to clear the headblock signal at one end of the stretch,operation of the code sending means for theopposite end of the stretchis also initiated, thereby applying driven code pulses to the trackrails at that opposite end which act to overcome any existing coding ofthe track circuits in a conflicting dimotion and thus cause clearing ofthe head-block signal and associated intermediate signals as requiredfor the desired direction of train movement.

Among other things, this method of determining the direction of trackcircuit coding by overpowering any existing track circuit code in aconflicting direction, in the manner characterizing this invention,permits manual control of the clearing of an intermediate signal in astretch of single track when desired to allow a train in this stretch tomake a back-up move with safety, the coding of the track circuits inthis instance being setup by the manual control for clearing thecorresponding entering signal governing train movement out of thestretch at the end to which backup movement is to be made. Similarly, inthe case of an outlying switch in the single track stretch, the desiredintermediate signals may be cleared under supervisory manual control toenable a train to move from this switch towards either end of thestretch, the coding of the track circuits in this case also being set upby a manual control to clear the corresponding entering signal.

For reasons relating to the use of the code type C. T. C. system forgoverning the direction of track circuit coding and more convenientlydiscussed later, it is proposed in accordance with this invention todetermine by manual supervisory control in a different manner thedirection of track circuit coding for the siding sections constitutingthe stretches of main track opposite the passing sidings. Generallyspeaking, when a manual control to clear the entering signal at eitherselected end of a siding section is exercised over the C. T. C. system,the desired direction of coding in this section is set up by acting uponthe coded track circuit equipment at the same end of the siding section,rather than at the opposite end as in the case of the stretch of singletrack between the ends of passin sidings. In the particular arrangementshown, the track circuit of the siding section is normally left codingin a predetermined prevailing direction to which it is automaticallyreset after each train movement, and coding in a direction opposite tothis prevailing direction is established when desired in response to amanual control to clear an entering signal by stopping such coding inthe prevailing direction at the transmitting end, provided the coding inthe prevailing direction is not being used to clear the other enteringsignal and inverse or oif code pulses are being received at saidtransmitting end.

Another feature of the invention relates to indicating automatically inthe remote control office of the C. T. C. system the occupied orunoccupied condition of the siding sections and the single trackstretches between the ends of the passing sidings. In the case of thesiding sections, a series or approach relay responsive to a wheel shuntis employed for governing the operation of the C. T. C. system totransmit an occupancy indication to the control oilice. In the case ofthe single track stretches, an indication control relay at each end ofthe stretch is arranged to be energized whenever the stretch becomesoccupied by a train to cause transmission of an occupancy indication tothe control office, and this relay is maintained energized until thestretch becomes unoccupied.

In another embodiment of the invention constituting a modification orvariation, instead of leaving the system normally coding after eachtrain movement to transmit code pulses suitable for clearing signals forone direction of train movement, provision is made to automatically stopor shut down the track circuit coding after each train movement, whensuch coding is no longer needed for signal clearing purposes, thisshut-down function being performed by transmitting a single shut-downpulse of limited dura tion, in opposition to the direction of codingleft behind a train, and thereby release the code sending relay thenenergized to cause the system to assume a normally deenergized andinactive condition. When it is required to clear some signal for adesired train movement after the system has thus been shut down,provision made for automatically initiating track circuit coding in theproper direction in response to the supervisory manual control of the C.T. C. systern to clear such signal. In the case of the single trackstretches between the ends of passing sid ngs. coding operation isinitiated after the system has been shut down at either selected end ofthe stretch when a signal clearing control is exercised by the C. T. C.system for the opposite end of the stretch; but in the case of thesiding sections opposite the passing sidings, track circuit coding inthe required direction is automatically initiated after the system hasbeen shut down by transmitting a start pulse over the track rails fromthe end of the siding section at which a signal clearing control isexercised by the C. T. C. system.

Since the track circuits and associated codin equipment are notenergized or operating in this other embodiment of the invention, exceptwhile signals are being cleared for some desired train movement, it isapparent that a substantial saving in current consumption and in thewear on the contacts and other moving parts of the coding equipment isobtained. This normally inactive or shut-down equipment of the inventionprovides for back-up train moves under supervisory manual control, fortrain movements into and out of outlying track switches, and for thetransmission of indications of occupany of the diiierent portions oftrack to the control office, and otherwise affords the same facility andsafety of train movement as in the normally coding form of theinvention.

Various other characteristic features, attributes and advantages of theinvention will be pointed out in detail hereinafter and will also beapparent as the description (progresses.

The accompany-ing drawings illustrate certain specific embodiments ofthe invention in a simplified and diagrammatic manner, and are arrangedto facilitate an explanation and understanding of the nature and mode ofoperation of the system rather than show in detail the construction andarrangements preferably employed in practice.

In describing the invention, reference will be made to the accompanyingdrawings in which those parts having similar features and functions aredesignated throughout the several illustrations by like letter referencecharacters which are generally made distinctive by reason of preceedingnumerals indicative of the location of the signal with which such partsare associated, and in which:

Figs. 1A, 1B, 1C and 1D, when arranged end to end, illustrate the systemof this invention as applied to a typical stretch of single trackbetween the ends of passing sidings and also one siding section;

Figs. 2A to 2F comprise a series of explanatory diagrams illustratingvarious operating characteristics of the embodiment of the inventionshown in Figs. 1A to 1D;

Fig.3 illustrates conventionally and diagrammatically the control paneland certain features of control equipment for a particular type of codedCTC system suitable for governing the signals and the direction of trackcircuit cod-ing for the embodiment of the invention shown in Fig. 1;

Fig. 4 shows diagrammatically a typical arrangement for the control of apower operated track track switch together with the time release sticklocking associated with such switch; and

Figs. 5A, 5B, 5C and 5D, when placed end to end, illustrate amodification of the system of the present invention and embodying theshut down feature mentioned above.

In these drawings relays and contacts have been shown in a conventionalmanner, and to facilitate the illustration in some instances thecontacts of relays are illustrated at a different place on the drawingsthan the winding of the relay. Also, to simplify the illustration ofcircuits, connections with the opposite terminals of a battery or othersuitable source of current for energizing local circuits have .beenrepresented by the symbols (-1-) and i-) associated with arrows.

General organization.-.For the specific embodiments of the inventionillustrated, it is assumed that the invention is applied to a typical orconventional single track railroad comprising single track stretchesbetween the ends oi passing sidings and siding sections constituting theportions of the main track opposite the passing sidings. It is alsoassumed that the switches at the ends of the passing sidings will bepower operated in the usual manner by switch machines under thesupervisory manual control of the C. T. C. system, although it should beunderstood that the system may be used in connection with hand operatedswitches.

Figs. 1A to 1D inclusive, when arranged end to end, show the apparatusand circuits for a single track stretch between the siding ends A and B,with starting or head-block signals I and IA, governing east-bound trainmovement into the stretch; starting signals 6 and 8A governing westboundtrain movement into the stretch; entering signals 2 and 2A governwest-bound train movements while entering signals 1 and 1A governeast-bound train movement out of the stretch over their respectiveswitches in normal or reverse positions; and two pairs of oppositeintermediate signals 3, 4, and 5, 6. At each siding end is a detectortrack circuit AT and BT, which is of the usual normally and steadilyenergized type. It should be understood that the arrangement andlocation of signals illustrated is merely typical and that the inventionmay be applied to other arrangements,

In the conventional arrangement of tracks for single track railroads asassumed, a siding section or portion of main track is associated witheach passing siding; and while the two ends of such siding sections.shown in Figs. 1A and ID are physically different portions of track, itis convenient to assume, in order to avoid unnecessary duplication ofdrawings, that the relays and circuits shown in these Figs. 1A and 1Bbelong to the opposite ends of the same siding section designated '!2 T,so that the circuit organication for one complete siding section isshown when Figs. 1D and 1A are arranged end to end.

These signals may be of any suitable type, but for simplicity in theillustration of their control circuits are assumed to be color lightsignals which display green, yellow, andred lights for proceed, caution,and stop indications when the lamps G, Y, and R- are lighted by thecircuits shown. Color light signals of the so-called search light type,such as disclosed, for example, in the patent to Field, No. 2,097,785,dated November 2, 1937, may be controlled from the same home and distantrelays H and D shown in the manner disclosed in my prior application,Ser. No. 439,520, filed April 18, 1941.

The starting of head-block signals l, IA, and 8, 8A and also theentering signals 2, 2A, and 7, IA, if power operated switches are used,are arranged to display in accordance, with established practiceabsolute stop-and-stay indications, while the intermediate signals 3, 4,5 and 6 are arranged to display permissive stop indications, such as bythe vertical or staggered relation of the signal light with a markerlight. In the embodiment of the invention shown, arrangement is made forapproach lighting the intermediate signals in .a manner later explained;and if desired the same expedient may be employed for approach lightingthe entering signals such as 2, 2A and the high speed starting signalssuch as I. The side track or portions thereof may also be equipped, ifdesired, with track circuits to provide approach lighting for the lowspeed signals i A and 8A governing train movement off of the siding.

The C. T. 0. system required for the control of the signals anddirection of track circuit coding may be of any suitable form capable ofgoverning the energization of signal clearing relays at the siding ends,and also controlling the power operation of the associated switchmachines ASM and BSM, if used. It has been assumed that the C. T. C.system will be of the code type acting to transmit during a controlcycle a series of distinctive code elements for station selection andswitch and signal control. This system also op.- erates during anindication cycle to send tothe .control office a series of distinctivecode elements identifying the particular field station sending, and alsoconstituting indications of switch position, signal clearing, and trackoccupancy. As a tangible example of a code C. T. C. system of thischaracter, it has been assumed that the apparatus and circuits asillustrated will be controlled by a two-Wire code C. T. C. system suchas disclosed in the patent to Hailes, et a1., Patent No. 2,259,561,granted October 21, 1941, and also illustrated and described inCentralized Traflic Control Handbook 20 of the General Rail way SignalCompany, copyrighted 194-1.

It is contemplated that the control ofiice equip ment of the C. T. C.system will include the usual control machine having on its controlpanel a miniature track diagram of the railroad, as diagrammaticallyillustrated in Fig. 3, with the usual two-position switch levers such asAWL and BWL for the switches at each end of the passing sidings;three-position signal levers such as AGL and BGL governing the signalsassociated with each siding end, together with suitable start buttonsASB and BSB associated with each lever group or panel. Indications ofthe switch operation may be displayed by a correspondence lamp in theswitch lever as disclosed in my prior Patent No. 2,038,128, dated April21, 1936, or in any other suitable manner. Indications of the clear orstop condition of the signals may be displayed by lamps located in thesignal levers or otherwise associated therewith or by lighting lamps inminiature representations of the signals on the track diagram asdisclosed for example in the patent to Phinney, No. 2,215,407, datedSeptember 17, 1940. In addition to the usual track occupancy lampsassociated with the detector track sections, it is proposed inaccordance with this invention to provide a lamp for each siding sectionand each single track stretch to indicate occupancy of these respectiveportions of the track when lighted. Fig. 3 also illustratesdiagrammatically a special arrangement of change and code determiningrelays governed by the start buttons which provides the desiredtransmission of control codes to diiierent field stations for thepurposes of this invention, as explained hereinafter.

Each of the siding sections andeach block between the signals isprovided with a coded track circuit equipment similar to and involvingthe same operating principles as the conventional and well-known codedtrack circuit. Each of these coded track circuits comprises a source ofcurrent (assumed to be a battery), a code following track relay TR, anda transmitter relay CTP for each end of the track section. The codetransmitter relay CTP is arranged to be operatively connected to codingcontacts C of a suitable code oscillator or equivalent which areintermittently operated in the usual way at a predetermined code rate;and when the transmitter relay is thus energized and deenergized itconnects the source of current and the track relay respectively acrossthe track rails alternately at a rate determined by the oscillatorcontacts with which the transmitter relay is then connected. Each trackrelay TR directly, or by the operation of a repeater relay, governs theenergization of a decoding transformer in the usual way to causeenergization of a signal control home relay H in response to the codingoperation of the track relay at any rate for giving a cautionindication, and causing energization of a signal control distant relay Din response to coding operation of the track relay at a predeterminedproceed or clear code rate, all in the manner that will be readilyapparent to those skilled in the art. It is assumed that code pulses atthe rate of '75 per minute will be employed for caution signal control,and at the rate of 120 for clear signal control, an extra clear coderate of, 180 being also preferably employed in connection. with the endtrack sections of the stretch for purposes later explained. These '75,120 and 180 code rates are determined by oscillator or coding contacts150, I280 and I800 respectively.

In one arrangement of control circuits for the intermediate signals, asshown in Figs. 1B and 10, there is only one H relay and one D relay foreach pair of intermediate signals; and these relays H and D govern theindications of one or the other of these signals selected in accordancewith the energization of coding direction relays WC and EC, which alsoperform the functions of directional stick relays for these signals.

The power operation of the switch and the clearing of, the signals ateach siding end in response to supervisory manual control may begoverned in any suitable manner by the C. T. C. system; and one typicalarrangement suitable for this purpose, based upon the disclosure of thepatent to Wells, Patent No. 2,159,922, May 23, 1939, is illustrated inFig. 4 for the siding end A.

Referring to this Fig. 4, the signal clearing relays ARD and ALD forgoverning the clearing of signals I, EA and 2, 2A for train movement tothe right and left respectively, and the switch control relays AWN orAWE controlling the power operation of the switch to the normal andreverse position respectively, are governed by the code C. T. C. systemin the manner fully explained in the Wells patent above mentioned, andfor the purpose of understanding the present invention a brief summaryof this operation will be sufiicient.

When the signal lever AGL in Fig. 3 is operated to the right or to theleft and a control code is transmitted, the lower winding of thecorresponding signal clearing relay ARD or ALD is energized for trainmovement in a corresponding direction to the right or to the left; andwhen a control code is transmitted with the signal lever ALG in themiddle or stop position, the relay vARD or ALD then energized ismanually restored to the deenergized position by the neutralization ordifferential action effected by energizing its upper winding.

Each signal clearing relay ARD and ALD has a stick circuit through itslower winding governed by a front contact 86 of the detector track relayATR and a back contact III of its slow repeater relay ATRP, so that therelay ARD or ALD then energized is automatically restored to itsdeenergized condition by the entrance of a train into the detector tracksection to drop the detector track relay ATR, and also so that either ofthese relays, if energized by C. T. C. control while the detector tracksection is occupied, will be held up after the train leaves, all in amanner more fully explained in the Wells patent above mentioned.

The switch control relays AWN and AWR are selectively energized by theC. T. C. code system in accordance with the operated position of theswitch lever AWL of Fig. 3, each of these relays being maintainedenergized by a stick circuit until the other is energized by manualcontrol. Also, the circuits for energizing the upper windings of therelay AWN or AWR by C. T. C. control include back contacts 53 and 55 ofthe signal clearing relays ARD- and ALD, so that no C. T. C. control tochange the position of the switch is effective while a signal clearingcontrol is exercised. I'hese switch control relays AWN and AWR. controlby their contacts ti and 52 the application of operating current to anelectrically operated switch machine ASM of the usual type to causepower operation of the switch to the corresponding normal or reverseposition, provided such operation is safe and a lock relay ALB, isenergized to close its front contact Gil.

When the position of the switch, as manifested by the condition of arelay AWP governed in the usual way in accordance with the position andlocked condition of the switch, matches the existing control exercisedby the switch control relay AWN or AWE then energized, a correspondingnormal or reverse correspondence relay ANCR or ARCR is energized bycircuits easily traced on the drawing; and these correspondence relaysANCR and ARCR govern the clearing of the associated signals in the usualmanner as illustrated in Fig. 1A.

While special provisions may be made for approach locking control of theswitch, such as by providing inverse codes in the manner disclosed forexample in my prior application, Ser. No. 439,520, filed April 18, 1942,above mentioned, in

the interests of simplicity, it has been assumed in the disclosure ofthe present invention that time release stick locking will be employed,and one typical arrangement for this purpose is diagrammatically shownin Fig. 4. Referring to Fig. 4, the power circuits for the switchmachine ASM, governed by the switch control relays AWN and AWR, areopened at the front contact of a lock relay ALR, when this relay isdeenergized by opening its normally closed circuit upon opening contacts63 and 64 by the release of either of the lock stick relays ILS or 21$for the signals 1, IA, and 2, 2A governing train movement over theswitch, or upon opening of contact 65 by the release of the detectortrack relay ATR. This energizing circuit for the lock relay ALPt may bereadily traced on the drawings.

The lock stitch relays ILS and ZLS and their associated time elementdevices ITE and ZTE, together with back contacts of the detector trackrelay, provide stick locking with time release and detector trackcircuit release in the well known manner. For example, when eithersignal relay IG or IAG is energized to clear the associated signal, thestick circuit for the relay ILS readily traced on the drawings throughcontacts 66, 61

and 68' is broken; and when the" signal is manually put to stop, currentis supplied through the back contact 68 of this relay ILS toits-timeelement device [TE to close its contacts 69" after a prescribed timeinterval to allow re-energization of the relay ILS. When the signal isput to stop by a train entering the detector track section, the backcontact H! of the detector track relay ATR allows the lock stick relayl-LS- to be re-energized immediately.

Although the circuits and apparatus of Fig. 4 has been described asassociated with the siding end A, it is to be clearly understood thatsimilar circuits and apparatus are assumed to be associated with sidingend B', and all others of a complete system. Also, all operationsmentioned in connection with this Fig. 4 are to be considered typicalof'all other siding ends.

Normal conditions-In the embodiment of the invention illustrated inFigs. 1A to 1D, driven code pulses are transmitted under normalconditions over the track rails of the track sections of the singletrack stretch-in a direction dependent upon the direction of the lasttrain movement through the stretch, as shown in the diagrams of FigsL 2Aand 2B; but for the showing in Figs. 1A to 1D it has been assumed thatthe last train movement through the stretch was east-bound leavin thetrack sections coding in a west-bound direction as indicated by thesolid arrows in said Figs. 1A to 1D as well as in the diagram of Fig.2A. Under normal conditions, driven code pulses are transmitted over thetrack rails of the siding section in a predetermined prevailingdirection assumed to be west-bound as shown in the diagrams of Figs. 2Aand 2B and indicated by the solid arrows in Figs. 1A and 1D; and thereare also inverse or off-cde pulses in the track rails of this sidingsection in the opposite direction as indicated by the dotted arrows inthose figures.

In many respects the arrangement of relays and operating circuits arethe same for the siding ends and intermediate signal locations; and itis convenientand helpful to assign the same reference numbers tocorresponding contacts for the differentrelays without differentiatingbe tween the locations where these contacts are used. Also, inconnection with the use of refer: ence numbers on the drawings, forthepurpose of convenient reference, a number of the wires and contacts inFig. 3 corresponding with those discl'osedin the Hailes, et al. PatentNo; 2259;561, October 2 1 1941, are given the same reference numbersuse'd in this patent; and the same is true for various parts shown inFig. 4 corresponding with those disclosed in the Wells Patent No.2,159,922, May 23, 1939.

The direction of coding in the single track stretch, under the normalconditions assumed, is due to thefact that the code sending stick relay8C8" in Fig. 1D, which was energized by manual control exercised by theC. T. C. system (in amanner later discussed) at the time the signalswerecl'eared for the prioreast-boundtrain move: ment' assumed, it beingmaintain-ed'energized by astickcircuit closed through the backcontact[2' of the code following track relay 8TB, and front contact l3 oflrelay8CS. With the code sending" relay 8'CS'thus i'naintained energized, thetrans-- mitter relay 8C'I'Pis intermittently energized at the '75' coderate by a circuit which may betraced from'(+) through front contact l4of'th lock stick relay BLS- associated with signals 8 and 8A codingcontactsof an oscillator 15C'operatingat I the-75 coder'ate, backcontact of signal relay 1G, front contact iii of relay 868 throughwinding of transmitter relay 8CTP, to I This applicationof driven codepulses atthe east end of the end track section 58T causes codingoperation of thecode following track relay 5TB, at the other end(seeFig. 10), which intermittently energizes through its front contactl8 a front contact repeater relay 5TP. The track repeater relay 5TP ismade su'liiciently slow releasing, while relatively q'uick to pick up inany suit-' able manner, as by being shunted by arectifier, so as to holdits front contacts closed during the coding operation ofthe track relay5TH.

With the trac'k relay repeater 5TP energized, the coding direction relay6W0 is energized by a pick-up circuit which maybe traced from (-jthroughfront contact 2-0 of relay 5TP, relay BWC, back contact 2| of othercoding direction relay 5E0, to Under these conditions, a quick actingtrack repeater relay 5---6'I"P is energized each time the track relay5TH. drops over acircuit closed from through back contact it of trackrelay warrant contact 22 of relay 5TP, back contact 23 ofrelay 5E6, andfront contact 24 of relay 6W0, windings of relay 5-6TP, to Theintermittentoperation of the contact finger 25 of the repeater relay5-6TP energizesalternately the two-lialves of the primary of thedecoding-transformer26, and causes intermittent energization of the homerelay 5+6H- by impulses in the secondary of thistransformer rectified byfront and back contacts of contact finger 21- of the repeater relay5-6TP in a manner familiar to those skilled in the art. The home relay5-6H has the usual slow release characteristics so as to maintain itsarmature steadily in the attracted position during the coding operationof the repeater relay 56TP;

With the relays BWCan'd 5.-- -6II energized, the

transmitter relay GC'I'P for the track section 3-6T is connected toadding contacts operatingat the rate through a circuit which may betraced from (+7) throughback contact I 3 of track relay 6TB, backcontact 22 of its slow release front-contact repeater 6'IP,codingcontacts IZllC,

front contact- 32 of relay 5-6H, and front contact 33 of relay 6W0,winding of codetransmitting relay GC TP, to I These driven codep'ulse'sapplied to the east or right-hand end of the track section 3-6?cause coding Operation of the code following track relay signal location5 result in the energiz'ation of the track relay repeater 3TP,'intermittent operation of the track repeater relay 34TP, andenergization of relays lWC and3-4H. Also, since'the proceed 120 coderate is being supplied to this track section 3-'-*6T, the relay 3-4Datsignal 3 is also energized through the agency of itstuned de-- codingcircuit and rectifier in the usual manner.

Under these conditions, with relays 4W0, 3-4H-and 3"4D at the signallocation 3 energ'ized, the transmitter relay 4CTP for track section I-4Tisoperated at the 1'80 code rate by a circuit similar to that describedfor signal location 5 and readily traced on the drawings through backcontacts I 8 and 22 of relays 'd'IR and 4TP, coding contacts I800, frontcontact to of distant relay 3--4D, front contacts. 32' and 33 of relays3-4H and 4'WC,.- relay 4C'I'P, to This causes coding operation of thetrack relay ITR in Fig; 1A and its quickacting repeater at the sidingend A thereby energizing relay I H,

3TH in Fig; 1B; and at the signal location 3 circuits similar to thosedescribed for and also relay lDX responsive to the 130 code rate. I v

Considering now the normal condition of cod ing in the siding section,and referring to Figs. 11) and 7A arranged end to end to show thecomplete siding, transmitter relay ZECTP at the east or right-hand endof the siding section 'l-2T is connected to the coding contactsoperating at the '75 code rate by a circuit which may be traced fromthrough a front contact 34 of the lock stick relay 2L5 for signals 2 and2A, coding contacts 150, back contact 35 of signal relay IG, frontcontact 36 of detector track relay ATR, back contact 31 of thecorrespondence relay ARCR, back contact 38 of a code reversing relay CR,relay ZCTP, to

This transmission of driven code pulses west for the prevailingdirection assumed over the track rails of the siding track section'l--2T causes coding operation of the track relay Wit and energizaticnof its slow release front contact repeater relay ITP, which in thisinstance is con nected in series with the upper half of the decodingtransformer. Likewise, signal control relay IE is energized, but not therelay 1]), since the '75 caution code rate is being transmitted.

Provision is also made for transmitting over the track rails of thesiding section inverse or oil code pulses for the purpose of providingan interlock between the opposing entering signals i and 2 as laterexplained. In the arrangement shown, these inverse code pulses arecreated by an impulse secondary winding H on the decoding transformer 12which acts each time the track relay 'ITR drops to provide a currentimpulse for momentarily energizing the transmitter relay 'ICTP over acircuit which may be traced from said impulse winding II through backcontact 13 of the signal clearing relay BRD, front contact '14 of thelock stick relay 'ILS, front contact 15 of repeater relay ITP,transmitter relay lCTP, to the same terminal. The transmitter relay 1CTPisof a biased polarized typeso that it is energized to operate itscontacts only by an impulse of the particular polarity which exists whenthe track relay 'ITR releases.

These inverse or off code pulses, which are transmitted in the usual wayduring the off intervals of the driven code in the siding track section,cause intermittent operation of the code following track relay 2TR (Fig.1A) at the opposite end of the siding section from which the driven codepulses are being transmitted, and through the usual decoding transformerconnection causes energization of the signal control relay 2H.

Under the normal conditions under discussion, the transmission ofwest-bound driven code pulses in the track sections of the single trackstretch and the energization of the west code direction relays 4W0 andBWC (Figs. 1B and 1C) prepare circuits for causing the intermediatesignals 3 and to display green or clear and yellow or cautionindications respectively as shown in the diagram of Fig. 2A; but thesesignals are preferably arranged as shown to be approach lighted, so thatno indications for these intermediate signals are actually shown. Thesignals at the siding ends are also at stop under normal conditions,since the signal clearing relays ARD and BED manually controlled by theC. T. C. system are deenergized, although driven codes are beingtransmitted in a direction to clear such signals for east-boundtrainmovements.

0'. T. C. control of signal clearing and direction of track circuitcoding-In accordance with this invention, when a supervisory manualcontrol is exercised over the C. T. C. system to clear a head-blocksignal at a selected end of the single track stretch between passingsidings, a control is likewise exercised to initiate operation of a codesending means at the opposite end of this single track stretch. Thisplan of operation is characteristic of the system disclosed in my priorapplication, Ser. No. 439,520, filed April 18, 1942; and if desired thesame organization disclosed in that application may be employed inconnection with the present invention to control the energization of thesignal clearing relay ARD or BLD at a selected end of the single trackstretch and on the same operating cycle of the C. 'I. C. system causeenergization of the code sending relay OS for the opposite end of thestretch. As a modification or variation of this method of C. T. C.control, the present disclosure employs a special arrangement ofstarting circuits in the control oilice, as illustrated in Fig. 3, so asto cause energization of a signal clearing relay ARD or BLD (Figs. 1Aand 10) at the C. T. C. field station at one siding end during oneoperating cycle, and energization of the code sending relay CS at the C.T. C. field station at the other siding end during another operatingcycle. In other words, in the arrangement disclosed, provision is madeto cause the code C. T. C. system to operate through two operatingcycles when the operator desires to send a train into the single trackstretch, and to transmit to one field station on one operating cycle asignal clearing control, and to a different field station during theother operating cycle a code starting control.

Considering this proposed organization of a code C. T. C. system, it isan operating characteristic of this type of system that during eachoperating cycle for transmission of controls one particular fieldstation is selected in accordance with the character of the codeelements transmitted during a number of station selecting steps,correspondin with a, particular group Of levers manually actuated by theoperator and requiring the transmission of new switch and/or signalcontrols.

In the particular type of code C. T. C. system disclosed in the patentto Hailes, et al. No. 2,259,561, October 21, 1941, and selected as thebasis for the present disclosure, the system is normally at rest and isset into operation by actuation of start buttons which control theenergization of a group of change and code determining relays so as totransmit control cycles in a predetermined sequence for the levershaving start buttons actuated. Also, in this particular system, thecharacter of the control elements for transmission of distinctivecontrols is determined by the polarity of energization of the linecircuit: and signal control codes for the energization and release ofrelays RD and LD for each field station are transmitted on two controlsteps, say for RD energization, for LD energization, and for stop signalcontrol, as explained fully in the patent to Wells, No. 2,159,922, May23, 1939. This leaves the code combination of on these signal controlsteps available for performing other functions; and in accordance withthis invention it is proposed use this extra control code for theenergization of the code sending stick relay CS associated with thecorresponding field station.

The additions and variations of the code C. T.

C. system disclosed in the patent to Hailes, et al., No. 2,259,561, foraccomplishing this purpose relate to the. starting and code determiningcircuits to provide for starting and transmission of this extra controlcode to the field station at one siding end when the start button forthe field station at the other siding end is actuatedv at a time whileits signal lever is positioned for train movement into the single trackstretch. For this purpose, the starting. and. code determining relaysand circuits in the control officeshown. in Fig. 2 of the Hailes PatentNo. 2,259,561 are modified as illustrated in the accompanying Fig. 3,more particularly by the addition of auxiliary change relays such asACHX for each field station group of levers.

Considering the operation of this control office equipment of Fig. 3 inthe case of a west-bound train movement, when the operator actuates-Startv button BSB, after positioning the. signal lever BGL to the left,the change relay BCH for the siding end B is energized in the usual wayand also the auxiliary change relay ACHX for the field station at theother siding end A is energized by a circuit from through contact 5| ofsignal lever BC-L to the left, contact 52 of start button BSE and lowerwinding of, relay ACHX, to and closing of the front contact 54. of relayACHX also causes energization of the regular change relay ACH throughthe normally closed contact 51 of the start botton ASB, winding of relayACH, normally closed contact of the cancel button CN, to (-)i.

In this w.ay,,uponactuation of the start button BSB, when the signallever; BGL is set to the left, the change relay ACH for the, field:station associated with the other end of the single track. stretch 1 andits. auxiliary change relay ACHX is also energized at the same time theregular change relay BCI-I is picked up. If the code C. T. C. system isat rest, or as soon as an existing operating cycle is completed, thecode determining relay such as ACD isenergized if its associated changerelay suchas ACE is energized, dependent upon the arrangement of theserelays in the-interlocking circuits. As illustrated, in accordance withthe disclosure of the Hailes, et al. patent, code determining relay BCDhas a priority in the sequence of control code transmission over codedetermining relay ACD; but the operation under consideration would besubstantially the same the priority were different by a differentarrangement of the interlocking circuits.

Referring to Fig. 3, and assuming the code C. T. C. system is at rest asshown, the energization of the change relay BCI-I by actuation of' thestart. button BSB as just described, closes a circuit to energize thecode determining relay 301) which may be traced from through backcontact M of, relay SC, back contact 42 of relay C, back contact 43 ofrelay CDS, front contact 44 of relay BCH, upper winding of relay BCD,through the cancel button CN to The energization of the relay BCD opensat its back contact 58 the stick circuit for the change relay BCI-I, andat the same time closes a front contact 59 to provide a stick circuitthrough the lower winding of relay IBCD in series with the relay CDS.Thus, while the change relay BCH is deenergized, therelay CDS isenergized to open its back contact 43' and prevent energization ofanyothercode determining relay. This operation is described'more in detailin the Hailes, et al. patent above mentioned.

When thecode determining relay BCD be-- lection and step 4 to switchmachine control. in.

conformity with the disclosure of the Haileset al. patent abovementioned, and that steps 5 and 5 corresponding with the energization ofstep relays V5 and V6 are utilized for signal control.

Under the conditions assumed, with the code determining relay BODenergized and the signal lever BGL set to the left-hand position, acontrol code of will be transmittedon steps 5 and 6 to the field stationat siding end B (Fig. 1D) to cause energization of the signal clearingrelay BLD- Considering how this particular polarity of these codeelements is determined, when the step relay V5 is energized, the relayNC giving acode element is energized by a circuit whichmay be tracedfrom through back contact of relay LV, back contact 32 of step relay V8,front contact 83 of step relay V5, code bus 85, front contact I83 ofrelay BCD, back contact I69 of relay BCHK, contacts of. signal lever BGLto the left, to bus all andrelay NC to A similar circuit for energizingthe relay PC giving a code elementis established on the sixth step whenstep relay V6 is energized.

Thus, under the particular conditions assumed, and with the arrangementof interlocking cir-- cuits' for the code determiningrelays illustrated,the first operatingv cycle of the systemv causes transmission of asignal clearing control code of to the field station at siding end B.

Whenthe relay LV in Fig.3 isenergized at the end of this operatingcycle, the opening. ofits back contact it, with. the relays C and-SCenergized' atthis time to open their back. contacts 48v and d9,interrupts the stick circuit for relay BCD in series with the relay CDS,thereby releasing relay'BCD and closing at. the back'contact d3 of relayCDS the circuit for: energizing code determining relay ACD through frontcontact 45 of relay ACH, when the operating cycle is completed and relayC and SC have released.

to close their back contacts 42' and M.

The energization of the code; determining re"- lay ACD opens at its backcontact Iii! the. stick circuit for the changerelayACH- and at the sametime establishes through its front contact :IM a.

supplemental stick circuit for the auxiliary change relay ACHX. The codeC; T. 0; system now operates in the regular manner. as described in theI-Iailes, et al. patent to select the field station at the other sidingend A, andtransmit on.

steps5, and 6 a control code of for. energization of the code sendingrelay iCS- at this.

siding end A (seelEFig. 1A).. The circuitfor energizing the relaycNC onsteptcorresponding with a code element may be. traced. from. throughback contact: 86 of relay LV, back contact82 ofstep relay V6, frontcontact 83- of step relay V5, code bus front contact 8'5; ofrelayACD,-front contact 8310!? relay ACHX t'o bus $0, and relay'NC to' therelay NC to givea code element on" the other. step 6. when relayrVii 5isy-energized is similarto that just traced.

A circuit for; energizing- An operation of the C. T. C. system similarto that just described occurs when the signal lever AGL is set to theright and the start button A83 is actuated, the change relay BCH for thefield station at the other siding end and its auxiliary change relayBCHX being energized by this start button, as well as its associatedchange relay ACH. In this case, due to the priority in the transmissionof control codes to the field stations by the interlocking circuits asillustrated, the signal clearing control is transmitted on the secondoperating cycle of the C. T. C. system, and the control to initiate thetrack circuit coding on a prior operating cycle; but it can beappreciated that the order in which the signal clearing and codestarting controls are transmitted is not material in the operation ofthe system, since the head-block signal being controlled cannot clearuntil a clearing track circuit code is received and also its signalclearing relay ARD or BLD is energized.

Operation for an east-bound train movement,-Having outlined the mode ofoperation with respect to the C. T. C. control for signal clearing andinitiation of track circuit coding for the single track stretch betweensidings, consideration may now be given to the operation of the systemfor typical train movements; and to illustrate certain operatingcharacteristics of the invention it is expedient to assume that, underthe normal operating conditions shown in the drawings, and with thetrack circuit coding existing in a direction for east-bound trainmovements, the operator desires to send another east-bound train fromthe siding end A of Fig. 1A to the siding end B of Fig. 1D, say from theside track at end A. To do this, the operator changes the position ofthe switch control lever AWL on the control panel in the control ofiice(Fig. 3) if necessary to cause the track switch to assume the desiredreverse position, sets the signal lever AGL to the right, and thenactuates the start button ASB. This causes transmission of a controlcode to energize the signal clearing relay ARD in Fig. 1A in the mannerabove explained, and also sends to the other field station at the sidingend B, a control code for energizing the code sending stick relay 808.

Under the conditions assumed, however, the relay 808 is alreadyenergized, so that such control code can perform no useful work, andrelay 8CS remains energized over its stick circuit.

Thus, driven code pulses are transmitted over the track sections of thesingle track stretch toward siding end A. This results in theenergization of the relays IH and IDX at siding end A (see Fig. 1A), sothat either the head-block signal I or IA may be cleared by manualcontrol over the C. T. C. system.

Referring to Fig. 1A and considering the operation occuring at sidingend A as a result of the energization of the signal clearing relay ARD,the closing of front contact 94 of this relay ARD closes the circuit toenergize relay IG or relay IAG to clear signal I or IA as the case maybe, dependent upon the position of the switch. In the case assumed, theswitch is supposed to be operated to the reverse position, and when thisoccurs, relay IAG is energized by a circuit which may be traced fromthrough back contact 9| of code sending relay ICS, front contact 92 ofsignal control relay IH, front contact 93 of detector track relay ATR,front contact 94 of relay ARD, back contact 95 of normal correspondencerelay ANCR, front contact 96 of reverse correspondence relay ARCR, relayIAG, to

Signal IA having thus been cleared, the train in question assumed to beon the siding may now advance into the detector track section AT. Thisreleases the relay ARD by opening front contact 80 of the detector trackrelay ATR before the back contact I I I of its slow release repeaterrelay ATRP closes, to provide stick signal control. The opening of frontcontact 93 of the detector track relay ATR also acts to deenergize relayIAG and put the signal IA to stop. This does not interfere with thecoding in the siding section, because under these conditions the reversecorrespondence relay ARCR. is energized, closing its front contact 31 toconnect the oscillator coding contacts to the transmitter relay ZCTPindependently of the position of the contact 36 of the detector trackrelay ATR.

When the east-bound train in question enters the first track sectionI-4T of the stretch of single track, it shunts the track relay ITR andstops its coding operation, thereby dropping relay ll-I to open at itsfront contact 92 the energizing circuit for signal relay IAG andmaintain signal IA at stop while this track section is occupied.

When the east-bound train in question enters the first track sectionI4T, or at least after it has advanced part way into this track section,depending upon operating conditions, the shunting effect of its Wheelsand axles increases the flow of current through the series relay 4SR atthe east end of this track section (see Fig. 1B) and causes this relayto close its front contact 91 and approach light the signal 3. Under theconditions assumed, the coding direction relay IWC is energized, and thehome relay 3-4H and the distant relay 34D are energized by the clearcode being transmitted west in track section 3-6T toward the signal 3,so that the green lamp of signal 3 is lighted over a circuit readilytraced through the front contacts 91, 98, 99 and I00 of the relays 48R,IWC, 34H, 3-4D.

In the arrangement shown, the series relay 48R upon closing its frontcontact I02 establishes a stick circuit for holding it energized as longas the wheel shunt exists independently of the coding operation of thetransmitter relay ICTP, this expedient being employed so that thisseries relay ISR does not need to have slow release characteristics tohold up during coding operation, or have a slow release repeater relay.In order that this series relay at 48R. may not erroneously energize itsassociated track relay, it opens at its back contact I03 the circuitthrough the code following track relay 4TB, this also incidentallyconstituting a check to assure that the series relay releases after eachtrain movement, otherwise no code can be received at the correspondingsignal location.

The energization of the series relay ISR also forms an auxiliary stickcircuit for the coding direction relay 4WC from through front contactI04 of relay lSR, back contact I05 of repeater relay ATP, front contactI06 of relay iWC, winding of this relay dWC, and back contact 2| ofrelay 3EC, to Consequently, when a train passes the signal 3 and shuntstrack relay 3TB and releases its repeater relay 3TP, the codingdirection relay 4W0 is maintained energized by this auxiliary stickcircuit until the signal relay 3-41-1 releases and closes at its backcontact I01 a permanent stick circuit readily traced for relay 4W0. In"this connection, it should be understood that the track relay repeaterST? is arranged to have a substantially shorter release time than thesignal relay 3-4H, say .6 of a second as compared with 1.5 seconds, sothat when the coding operation of the track relay 3TH ceases under othercircumstances when the series relay ish. is not energized by anapproaching train, the coding direction relay 4W6 drops, because itspick up circuit is broken at the front contact 20 of relay 312? beforeits stick circuit is established at the back contact 10'! of relay 34H.

By reason of this special control of the coding direction relay 4W0, itperforms the functions of a directional stick relay as commonly employedin single track signaling systems; and after the east-bound train inquestion has passed entirely into the track section '3 G-T in advance ofthe signal 3, a code at the 75 rate is delivered to the track sect-ionl-4T in the rear of this signal with the relay'dWC energized to closeits front contact 33, and the relay -3--4H deenergized closing its backcontact 32, thereby providing a caution code in the rear of theeastbound signal 3 to permit the head-block signal l or 1A to be clearedfor a following train movement if desired, as shown in the diagram ofFig. 20.

When the east-bound train in question enters track section 3'5T, theseries relay BSR for the east end of this track section is energized toapproach light the signal (Fig. 1C) and provide an auxiliary stickcircuit for the relay 6W0 in the same manner just explained. Under thenormal conditions as shown in the diagram of Fig. 20, the signal 5 willdisplay a caution in dication, since the entering signals 7 and l'A areat stop; but under ordinary circumstances the operator will havepreviously positioned the switch and signal levers for the siding end Bto clear one of the entering signals 1 or 7A for the train in questionto enter the siding section or passing siding, as the case may be.

Assume, for example, that the operator causes energization of the signalclearing relay BRD (see Fig. 1D) for movement of the east-bound train inquestion into the siding section. The closing of the front contact ofthis relay BRD closes 'a circuit for energizing signal relay 1G to clearsignal I, which may be traced from through front contact H2 of relayBRD, front contact H3 of detector relay BTR, front contact H4 of normalcorrespondence relay BNCR, relay 7G, front contact H5 of signal controlrelay lI-I and front contact H6 of relay VIP, to Since the normalprevailing direction of coding inthe siding section is west-bound andsignal control relay 1H is energized, the entering signal 1 may becleared Without modifying the direction of coding in the siding section.In a similar way, the low speed or diverging signal IA may be cleared byenergizatlon of signal relay 'IAG upon energization of the signalclearing relay BBB and closing of its front contact H2 if the switch isoperated to the reverse position to close front contact H3 of thereverse correspondence relay BRCR.

When the east-bound train under consideration approaches signal 5, thissignal should indicate caution if both of the entering signals 1 and 1Aare at stop, or if the entering signal 1A has been cleared by theoperator for a train movement into the siding, and should indicate clearonly if the entering signal 1 has been cleared by the operator for atrain movement into the siding section over the switch in the normalposition. Thus, as shown in Fig. 1D, the code rates for governingthe'clear and caution indications of the signal Q5 are selectedfby frontand back contacts l5 of the signal relay IG. H I H When the'eastbourid'train'in'question passes the intermediate signal 5, as shown inthe diagram of Fig. 2D, 2. '75 code rate is transmitted to theintermediate signal 3in the rear, and the coding operation of the "trackrelay 3TB, (Fig. 1B) picks "up its repeaterjrjelay 3T1? to close itsfront contactv 2'0 and'hold up the relay 4WC by its pick-up circuit,"and also causesene'rgization of the "relay 3-4I-I tom-crease the coderate in the track section 't--QT to the clear rate of 120,

, thereby permitting the head-block signal i to give a clear indicationfor a following train movement if desired. It will be noted that thecontrol circuits for the i si'gnal 1 se e Fig. 1 are organized so thatthe green lampjG is lighted by the energization of either of thedecoding relays ID and IDX responsive respectively to 120 an 1. 0 c deate When the east-bou nd train under consideran P ss s t e er ssis al 1e c th tector track section B'I' fatthe siding end 13 (see 13). h h ntinthe detect r tra k.- lay B R, elea e he S g al cle r la B in the usualway, and a'lso opens at its front contact ,1 I13 the energizing circuitfor signal relay 'lG soas to hold the signal 1 at stop whilethedetectortrack-section is occupied, even though the relay BRD might beagain energized by a subsequent C. C. control code, and although thetrain being short or a single locomotive, has not advanced into thesiding section to drop the signal control relay lH.

When the east+bound train in question enters the siding track section1521, cessation of the coding operation of the tra'cl; relay 1TBreleases its slowrelease-repeater relay FTP to connect the codetransmitter rel'ay ICTP through the back a t; 1 ofv e y 'lfhhack 'ntact1.2.0 ofrelay 8G, codingcontactsltC, andfron't contact l2! of relay 3TB,and thus permit relay TICTP to be intermittently operated when the trainleaves the detector track section and front contact I21 of thedetectortrack relay BTB closes, thereby producing driven code pulsesunder and followins the tra n... H

Considering the operation for the movement of the east-bound train underconsiderationout of the siding section; and arranging Figs. 1D and 1Aend to end to show the circuits for the complete siding; assume that thehead-blocksignal I has been cleared to permit the east bound train underconsideration in the siding track section l-2T to ad ance When thistrain drops the detector track relayA'IR, the transmitter'relay ZCTP issteadily energized by a circuit from through the back contact 36 ofdetector track relay ATR, back contact 31 of correspondence relay ARCR(switch being normal to permit sig-. nal l to clear), back contact 38 ofrelay CR, and relay ZCTP, to When the train clears the siding tracksection l- 2'I this steady energization of the transn'iitter relay 2011?is effec tive during the first ofi period of the driven code beingtransmitted from the other end to energize me track relay lTR'andits reeater relay FTP to cut oii at the back contact "l5 of relay 'lTPsuchdriven codebeing transmitted in the reverse direction; soon as the trainleaves

